Apparatus to make cast iron with spheroidal graphite

ABSTRACT

To provide controlled access of molten iron to magnesium which is covered with a protective layer, a plug-like body is introduced in contact with the magnesium, extending through the covering layer (preferably calcium carbide). When the molten iron is poured into the container, the plug-like body will melt by contact with the molten iron, thus providing controlled exposure of the molten iron to the magnesium. To further control the process, the plug-like body can extend beyond the protective covering layer and, itself, be covered with a protective sheath of refractory material which can be lifted off from the body when the exposure is desired. The lift-off mechanism can be used to introduce the plug-like body by providing therein a mechanical or magnetic holding arrangement.

United States Patent [191 Anders et al.-

[111 3,802,680 Apr. 9, 1974 APPARATUS TO MAKE CAST IRON WITH SPHEROIDAL GRAPHITE [73] Assignee: Georg Fischer Aktiengesellschaft,

Schaffhausen, Switzerland 22 Filed: Mar. 21, 1972 21 Appl. No.: 236,743 g [30] Foreign Application Priority Data 75/56-58, 130 R, 130 A, 130 BB, 130 AB, l30 BA, 130 C, 53

[56] v References Cited 7 I UNITED STATES PATENTS 2,776,206 l/l957 Klingbeil 75/93 FOREIGN PATENTS OR APPLICATIONS 692,765 8/1964 Canada 75/130 R Primary Examiner--Gerald A. Dost Attorney, Agent, or FirmFlynn & Frishauf [5 7] ABSTRACT To provide controlled access of molten iron to magnesium which is covered with a protective layer, a pluglike body is introduced in contact with the magnesium, extending through the covering layer (preferably calcium carbide). When the molten iron is poured into the container, the plug-like body will melt by contact with the molten iron, thus providing controlled exposure of the molten iron to the magnesium. To further control the process, the plug-like body can extend beyond the protective covering layer and, itself, be cov ered with a protective sheath of refractory material which can'be lifted off from the body when the exposure is desired. The lift-off mechanism can be used to introduce the plug-like body by providing therein a mechanical or magnetic. holding arrangement.

8 Claims, 3 Drawing Figures APPARATUS TO MAKE CAST IRON WITH SPHEROIDAL GRAPHITE The present invention relates to to an apparatus to make cast iron with spheroidal graphite, by treating the cast iron, when liquid, with metallic magnesium or a magnesium alloy.

It has been proposed to introduce magnesium or magnesium alloy into a depression, or compartment formed in the container, or ladle, in which it is to be contacted with the iron, and to cover the magnesium or magnesium alloy with a protective layer. This protective layer may consist of steel chips, or steel pieces. Re action between the magnesium and the liquid cast iron will be delayed, upon filling of the container, until the protective layer has been dissolved by the liquid iron, so that the liquid iron may contact the magnesium. The time delay until the reaction between the liquid iron and the magnesium starts is difficult to be controlled in this system, since different parameters such as temperature of the liquid cast iron, thickness of the protective layer and temperature of the container or ladle have a definite influence on the delay time. The greatly varying delay time between the beginning of the reaction is undesirable in a foundry operation since then the reaction of the magnesium with the cast iron is subject to great variations.

It has, therefore, already been proposed to cover the magnesium or the magnesium alloy with a protective layer of calcium carbide, or some other material, and to mechanically destroy this protective layer at a predetermined period of time, for example by means of a rod or the like, in order to provide controlled access of the molten cast iron to the magnesium.

If a protective layer of calcium carbide is used, it has also been proposed to introduce gas under pressure through aporous plug from the outside of the container, in order to break up this protective layer and permit access of the molten iron to the magnesium. Destruction of the protective layer of calcium carbide by mechanical means or by pressure forces permits an exact point of time at which the reaction, or the treatment between the magnesium and the cast iron will start. Still, undesirable differences in the reactive process may arise since the contact area between the molten cast iron and the calcium carbide is subject to great variation, and cannot be controlled beforehand.

It is an object of the present invention to provide apparatus in which the reaction between magnesium and molten iron can be delayed to a predetermined time, so that it can start at a predetermined instance, while, at the same time, the contact area between the molten iron and the magnesium is controllable.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, a protective layer such as calcium carbide (CaC) covers a layer of magnesium. Embedded in the calcium carbide is a cylindrical, or prismatic plug-like body made of iron, or iron alloy, extending therefrom or at least having an exposed face. This plug-like body is applied against the magnesium so that, upon contacting of the body with the molten iron, this body itselfwill melt and the reaction between the liquid iron and the magnesium, or the magnesium alloy can commence. The contact area between the liquid iron and the magnesium is, of course, given by the cross-sectional area of this body.

The delay time between introduction of the molten iron and start of the reaction can be accurately controlled if a refractorysheath is provided which covers the plug-like body, or the portion thereof extending be-' yond the protective layer, the sheath being lifted off after the liquid iron has been filled into the container and when the reaction is .to start. The plug-like body preferably is held by a paraIlelogram-rod-link arrangement and can, additionally, be provided with means to releasably secure the plug-like body thereto so it can be used as an insertion element to insert the plug-like body into the container and against the magnesium layer, prior to the start of the process steps.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic longitudinal section through a container illustrating the method and the apparatus, in one embodiment;

FIG. 2 is a view similar to FIG. 1., illustrating a modified embodiment; and

FIG. 3 is a fragmentary view illustrating the lower part of the sheath and the plug-like body.

Acontainer l, which may be a ladle, has a depression 2 formed in the bottom thereof. The container 1 has a plug 3 therein which consists of a core 8 with a ceramic, refractory sheath 13. The plug 3 is secured by means of a parallel-linkage arrangement 9. Magnesium, or magnesium alloy 5 is introduced into the depression 2. It is covered by a protective covering layer 6, for ex; ample granular calcium carbide. Liquid iron 10 is introduced into container 1 at an inlet 7, in such a manner that the protective covering is not destroyed. This is well known in the art.

Magnesium, or a magnesium alloy such as magnesium silicate or magnesium ferrosilicate is introduced into the depression 2 in the bottom of container 1. A body 4 of iron or iron alloy, in the form of a cylinder,

is placed into the layer of magnesium 5. A protective layer 6 is then placed thereover, preferably such that the upper surface of protective layer 6 is flush with the upper surface of body 4. Liquid iron is then introduced into the container 1 from the inlet 7. By suitable dimensioning of the body 4, and of the thickness of the protective layer 6, the delay time for the reaction, that is, the time between start of introduction of molten iron until the reaction begins, can be predetermined and set within certain limits. Providing a plug 3 which covers the top surface of body 4 substantially increases the time until a reaction with the magnesium will start. Plug 3 should at least cover the top surface of the body 4, but may extend also over the protective layer 6 (see FIG. 1). If a plug 3 is used, the plug is lifted by means of its lifting mechanism 9, permitting free access of the molten iron 10 to the plug-like body 4, which will melt and, upon melting, permit exposure of the magnesium or magnesium alloy 5 with the molten iron.

In the embodiment of FIG. 2, the container 21 is formed with a partition wall 22 at the bottom thereof, to provide a separated portion, or subsidiary vessel into which magnesium or magnesium alloy 25 can be introduced. The plug-like body 24, preferably a cylinder or a prism, is so placed within the magnesium that the upper portion of the body 24 extends somewhat over and beyond the protective layer 26. A plug 23 is formed of a core 28 with a refractory covering 30, suspended by a parallel link suspension 29. The plug 23 is formed with a recess 27 at its bottom which is big enough in order to accept the portion of body 24 extending beyond protective layer 26. Molten iron is introduced at an inlet point 31. 9

Operation according to FIG. 2: The magnesium 25 and body 24 are introduced into the auxiliary compartment; a cover layer 26 is placed thereover. Thereafter, the plug 23 is lowered until the recess 27 completely covers the projecting portion of the body 24. This recess 27 can be so formed that the plug 23 extends down to the magnesium 25. Molten iron 32 is introduced through inlet 31. The treatment commences upon lifting of plug 23. After the time gap determined by melting or dissolution of body 24, reaction between the iron melt 32 and the magnesium will start.

The body 34 can be introduced into the vessel by means of the plug holder. As seen in FIG. 3, a holding device which can be mechanical or magnetic for the body 34 is provided in the interior of plug 39. A magnet 36 is located in the interior of the plug 39, protected against influence of the iron melt 32 by a ceramic protective wall 35. A rod 38 is guided in the interior of plug 39 to move the magnet to bring it close to, or lift it off from plug 34, so that it can be rendered effective or ineffective. The entire arrangement is located within the interior of the plug 39 and is used in order to hold the body 34 after its introduction into the recess 37, until the magnesium 25 and the protective layer 26 have been introduced in the auxiliary compartment. Upon begin of the introduction of molten iron 32, the magnet 36 is disabled from continuing to hold the plug 34 by lifting of rod 38. Thereafter, plug 39 can be moved or lifted as desired by the process, as described in connection with plug 23.

Rather than providing for a magnet, the iron or iron alloy body 34 can be held within the recess 37 of plug 39 by a slight interference fit, the recess 37 tapering slightly upwardly, so that, after placement of the body 34, pushing on rod 38 will release the body 34 from holding contact with plug 39. This arrangement can be combined with a magnet (FIG. 3), where the interference fit is not shown for purposes of simplicity in the drawing.

The begin of the reaction, as well as the reaction process itself, can be completely controlled within wide and accurate limits so that the resulting cast iron will be of uniform and predetermined quality and characteristics.

Various changes and modifications may be made within the inventive concept.

We claim:

1. Apparatus to make cast iron with spheroidal graphite comprising a container (1);

a layer of magnesium or magnesium alloy in the container;

a protective covering layer (6) covering the layer of magnesium or magnesium alloy;

a plug-like body (4) of iron or iron alloy located in contact with said magnesium or magnesium alloy and extending through the protective layer (6) to be exposed at the outer face thereof, said body, upon introduction of molten iron and contact of its exposed portion with the molten iron, melting, and permitting controlled contact of the molten iron with the magnesium;

a covering sheath (3, 13; 23; 39) movably located to shield the exposed portion of said plug-like body from contact with the molten iron;

and means (8, 9; 29) movably supporting said sheath to permit removal of said sheath from protective shielding position and contact of the molten iron with the plug-like body.

2. Apparatus according to claim 1, wherein the movable suspension means comprises a parallel rod-linkage suspension.

3. Apparatus according to claim 1, wherein the pluglike body extends beyond the protective covering layer, said covering sheath being formed with a recess (27) into which the portion projecting beyond the covering layer fits.

4. Apparatus according to claim 1, comprising means in the covering sheath removably holding the plug-like body to permit use of the movable sheath as a holding element for the body.

5. Apparatus according to claim 4, wherein the holding means comprises magnetic means.

6. Apparatus according to claim 4, wherein the holding means comprises mechanical means.

7. Apparatus according to claim 1, wherein the container is formed with a compartment at the bottom thereof, the magnesium being located in said compartment, and a movable plug of refractory material is provided movable in line with said container between covering and uncovering position with respect to said pluglike body.

8. Apparatus to make cast iron with spheroidal graphite comprising 7' a container (1);

a layer (5) of magnesium or magnesium alloy in the container;

a protective covering layer (6) covering the layer of magnesium or magnesium alloy; and

a plug-like body (4) of iron or iron alloy located in contact with said magnesium or magnesium alloy and extending through the protective layer (6) to be exposed at the outer face thereof, said body, upon introduction of molten iron and contact of its exposed portion with the molten iron, melting, and permitting controlled contact of the molten iron with the magnesium;

wherein the container is formed with a compartment at the bottom thereof, the magnesium being located in said compartment, and a movable plug of refractory material is provided movable in line with said container between covering and uncovering position with respect to said plug-like body.

lovent fl l Georg ANDERES et a1 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Farm: No- 3.802.680 Date Avril 9 1974 It is certified that error appears in the above-ideotified patent and that said Letters Patent are hereby corrected as shown below:

Please correct the first inventor's last name ta read as follows:

-- Georg ANDERES Signed and sealed this 1st day of October 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM Po-1050 (10-69) 

2. Apparatus according to claim 1, wherein the movable suspension means comprises a parallel rod-linkage suspension.
 3. Apparatus according to claim 1, wherein the plug-like body extends beyond the protective covering layer, said covering sheath being formed with a recess (27) into which the portion projecting beyond the covering layer fits.
 4. Apparatus according to claim 1, comprising mEans in the covering sheath removably holding the plug-like body to permit use of the movable sheath as a holding element for the body.
 5. Apparatus according to claim 4, wherein the holding means comprises magnetic means.
 6. Apparatus according to claim 4, wherein the holding means comprises mechanical means.
 7. Apparatus according to claim 1, wherein the container is formed with a compartment at the bottom thereof, the magnesium being located in said compartment, and a movable plug of refractory material is provided movable in line with said container between covering and uncovering position with respect to said plug-like body.
 8. Apparatus to make cast iron with spheroidal graphite comprising a container (1); a layer (5) of magnesium or magnesium alloy in the container; a protective covering layer (6) covering the layer of magnesium or magnesium alloy; and a plug-like body (4) of iron or iron alloy located in contact with said magnesium or magnesium alloy and extending through the protective layer (6) to be exposed at the outer face thereof, said body, upon introduction of molten iron and contact of its exposed portion with the molten iron, melting, and permitting controlled contact of the molten iron with the magnesium; wherein the container is formed with a compartment at the bottom thereof, the magnesium being located in said compartment, and a movable plug of refractory material is provided movable in line with said container between covering and uncovering position with respect to said plug-like body. 